Railroad trains in North America, Europe and substantial parts of the world are equipped with some form of automatic pneumatic brake systems, sometimes referred to as "air brakes." Air brakes provide a reliable and generally fail-safe system for permitting the engineer, conductor or other train crew to apply the brakes throughout the train as well on the locomotive. Air brake systems are continuous power brake systems having an air compressor on the locomotive connected to a brake pipe extending throughout the train. The locomotive includes an automatic brake valve. The engineer uses the automatic brake valve to reduce the air pressure in the brake pipe to apply the brakes, or to increase the air pressure in the brake pipe to release the brakes. Each railroad car in the train has a control valve which senses a "reduction" or "increase" of air pressure in the brake pipe, and applies or releases the brakes according to the "reduction" or "increase" command, respectively. The control valves vary in construction and in operating features to suit freight or passenger trains.
While air brakes are used on both freight and passenger trains, the demands on each system are quite different due to the length of the train, the weight of the train, the speed of the train and other factors. The length of the train is especially important since air pressure reductions in the brake pipe travel at approximately the speed of sound. In a long freight train, such as one having one hundred fifty cars and a possible length of one and one-half miles, it takes approximately eighteen seconds for an air pressure reduction initiated in the locomotive to reach the last car in the train. Accordingly, in the known automatic pneumatic brake systems on freight trains, the build-up of brake cylinder pressure has to be carefully retarded in the front cars to prevent the last cars of the train, where the brakes have not yet been applied due to the signal delay, from running into the front cars. Consequently, full pressure braking is delayed and braking distances are longer. On shorter trains such as passenger trains, this is not such a significant problem, even though there is some delay between the braking of the first and last cars.
To solve these problems, electronically controlled pneumatic brake systems have been proposed and are currently being developed and tested. Electronically controlled pneumatic brake systems generally include a computer controlled network wherein the locomotive is equipped with a head end unit or a master controller for controlling braking throughout the train, and each car is equipped with a car control device for controlling braking on the car based on signals from the master controller. The electronically controlled pneumatic brake system provides substantially instantaneous and simultaneous brake signals to all of the cars in the train, which enables all of the cars to brake at substantially the same time (i.e., increasing the rate of brake cylinder pressure build-up). Electronically controlled pneumatic brake systems incorporate many of the parts of the automatic pneumatic brake system equipment including the brake pipe, the reservoir tanks, the pipe bracket, the brake cylinder(s) and the rigging or linkage between the brake cylinder and the brakes. The car control devices include pneumatic devices (such as solenoid actuated pneumatic valves) which are suitably attached to one or more manifolds mounted on the existing pipe bracket.
Various manifolds for electronically controlled pneumatic braking systems have been suggested using multiple plates. Some of the problems associated with manifolds having two or three plates are described in detail in U.S. Pat. No. 5,803,124. Generally, prior manifold designs allowed the adhesive which was used to bond the plates of the manifold together to sometimes block the narrow channels, and required channels with circuitous paths to avoid the crossing or overlapping of channels. U.S. Pat. No. 5,803,124 discloses a three plate manifold which purportedly solves these problems by providing a first plate with chambers and passageways on its interior surface, a second plate with chambers and passageways on its interior surface and a center plate abutting the interior surfaces of the first and second plates and having apertures extending through the plate connecting the chambers and passageways in the first and second plates. The separation of the passageways and chambers in the first and second plates by the center plate facilitates straighter paths for the passageways and larger passageways which are not be blocked by excess adhesive.
However, there is a need for other manifold constructions which eliminate the adhesive problem, allow for overlapping channels and chambers, reduce the amount of machining of large plates, include alignment means for assembly of the plates and provide other advantages as described herein.